The invention relates to a device for adjusting penetration depths of a prescoring saw blade for prescoring the underside of workpiece panels during advance of the carriage of a movable sawing unit, wherein the prescoring saw blade is arranged upon a movable support and wherein the position of the prescoring saw blade changes in response to the motion of a tactile element, moving along a directing surface, which tactile element is associated with the prescoring saw blade.
Panel splitting saws usually comprise a sawing unit which is movable below a table and includes a circular saw blade and a preceding prescoring saw blade. These emerge from the workpiece supporting surface of the panel splitting saw in the direction of advance when the severing cut is being made.
By the prescoring saw blade first penetrating the underside of a workpiece panel along the severing plane at a depth of only a few millimeters during the advancing motion, it is ensured that the actual severing cut made by the circular saw blade cannot cause splintering at the lower edges of the severed surfaces of the workpiece.
If the workpiece panels which are to be split up are rounded off along one or two panel edges extending perpendicularly to the severing plane and parallel to the panel supporting surface, in their upper edge region, and are possibly also laminated (postforming) on their entire upper surface, the prescore groove extending in the workpiece panel must be of special configuration in the region of that rounded-off panel edge which is last severed during a severing cut. In particular, it must be ensured that the panel material in the surface region of this panel edge which is of convex curved cross-section cannot be splintered by the circular saw blade emerging from the panel edge.
This is effectively prevented by the penetration depth of the prescoring saw blade being successively increased in the end phase of the advancing motion in such a way that in relation to the cross-section of this panel edge, the prescore groove emerges from the workpiece panel precisely at the transition point between the rounded-off end face portion and the upper planar panel surface.
To achieve this, a support guided in a vertically displaceable manner in the sawing unit and carrying the prescoring saw blade and its drive has a tactile element which in the end phase of the advancing motion of the sawing unit strikes a stationary directing surface which is of such configuration that the necessary lifting motion of the support and the prescoring blade, respectively, is effected.
Prior to cooperation of the tactile element and the directing surface, i.e., at the beginning of a severing operation, the support is driven out of a lower initial position into a first intermediate position in which the prescoring saw blade penetrates only slightly, for example, at a depth of 1 millimeter, the underside of the workpiece panel in the region of the panel edge which is to be severed first. It is then driven into a second intermediate position which it maintains throughout the greater part of the path of advance and makes a prescore groove at a depth of, for example, 3 to 5 mm before it is finally driven upwardly out of this intermediate position by the directing surface and the tactile element, in the manner described above, in order to sever the other panel edge.
The precision of the cutting motion of the prescoring saw blade achieved in the end phase of the advancing motion by the controlling motion of the support effected by the tactile element sliding along the directing surface has up, to an advancing speed of approximately 50 m/min, so far been sufficient to ensure that the prescore groove emerges from the workpiece panel at the panel edge surface which is rounded off in its upper region, at the point of transition between the rounded-off edge surface portion and the upper planar panel surface.
However, this type of support control does not permit the advancing speed to be substantially increased, for example, to 120 m/min, without the point at which the prescore groove emerges at the top of the workpiece panel simultaneously being displaced. This is due to elasticities and inertias of the masses to be moved when the tactile element strikes the directing surface and also results in a impact effect caused by the parts striking one another, which disadvantageously affects both the cutting quality and the service life of the cooperating parts.
The object underlying the invention is, therefore, to improve a movable sawing unit, having a prescoring saw blade mounted on a vertically movable support and including a tactile element for controlling vertical movement of the support, by providing a device for coordinating the rate of the vertical movement of the support with the rate of advance of the severing saw blade to ensure that the prescoring blade emerges from the top of the trailing edge of the panel being severed, thereby reducing the likelihood of splintering.
This and other objects of the invention will become apparent in light of the present specification, drawings and claims.